1. Field of the Invention
This invention relates to apparatus for cutting wood, and in particular to apparatus for cutting laminated wood structures such as doors, paneling and plywood.
2. Discussion of the Prior Art
Often it is necessary to use power saws to cut wood in directions perpendicular or at large angles to the wood grain. Crosscut saw blades having a relatively few large teeth are especially designed for this purpose and provide rapid cutting. However, because of their configuration, crosscut blades tend to produce cuts having ragged and splintered surface edges. Such splintering and tearing of the surface wood is generally due to the surface layer or surface fibers of the wood having insufficient support or backing to withstand the cutting stresses. Thus, as the blade advances, the surface fibers are pushed upwardly and torn off, rather than being smoothly cut. This problem is particularly acute in thinly laminated materials, such as hollow core doors and plywood paneling, because the thin top layer of wood is only glued to the remaining composite structures; as a result, it tends to readily separate at the glued interface.
Various methods have been used to enable relatively clean, smooth cutting of wood laminates without tearing the surface fibers. For example, plywood-type saw blades are often used. These blades are typically hollow ground to minimize edge contact and have a large number of closely spaced teeth. Because the relatively small amount of wood cut by each tooth includes only a relatively small number of parallel surface fibers, the lifting action of the blade on the wood surface fibers is reduced, thereby reducing the extent of surface splintering. However, the splintering is not entirely eliminated. Because cutting action of such blades, due to their small bite, is slow, the cutting time for large panels and sheets of plywood is substantially increased over the time required using crosscut blades.
In addition, because plywood type blades are generally unavailable in high carbon steel, wear is relatively rapid and the blades are easily damaged when, for example, they encounter metal staples commonly used in constructing hollow core doors.
Ragged cut edges can, however, be eliminated if the surface fibers of the wood are cut prior to sawing the rest of the wood. Such cutting (or weakening) of surface fibers of wood is commonly called "scarfing." A typical method of scarfing heretofore used has been to manually mark the cut line and then cut or deeply indent the wood surface with a knife prior to making the cut with a power saw. However, this method is slow since the scarfing takes additional time and is a separate operation from the actual sawing. Also, because the scarfing is done separately, accurate, and often elaborate means are required to assure that the edge or edges of the saw blade cut will exactly coincide with the previously scarfed line or lines. Otherwise, not only will surface tearing still occur, but the scarfing lines may also be visable after the cut. This alignment is made even more difficult, and time consuming, when the cut is to be made blind, that is, with the scarfed lines facing a support table as is often necessary using fixed circle saws.